The invention relates to a spring element for compensating for axial play in a motor shaft of an electric motor, as generically defined by the preamble to the main claim.
Motor shafts of known electric motors are supported with axial play in a motor housing. The axial play in the motor shaft is necessary because of or also as a result of manufacturing tolerances. In addition, an axial play in the motor shaft and the motor housing is necessary because of the different thermal expansions of the motor shaft and the motor housing. The axial play in the motor shaft results in noise that is partially a function of the position of the electric motor and in part, leads to distinctly audible impact noises during changes in the rotation direction of the electric motor. In addition, axial vibrations of the armature can occur, which result in noise and increased wear.
For this reason, efforts have been made to compensate for the axial play in the motor shaft through the use of spring elements. Thus, for example, U.S. Pat. No. 2,307,772 has proposed placing a convex spring washer onto the motor shaft as a spring element, which is supported against a motor shaft bearing and an armature that is affixed to the shaft and as a result, compensates for axial play in the motor shaft. However, a large number of parts is required in order to install the spring washer. The spring washer is connected to two flat support washers and parts are provided, which secure the spring washer to the motor shaft in a non-rotatable, axially movable fashion. The known spring element is therefore complex and expensive with regard to manufacture and installation.
The spring element according to the invention, with the features of claim 1, has a stop disk with which it is axially supported, for example against a shaft bearing of the motor shaft of the electric motor. One or more spring arms are connected to the motor shaft and are of one piece with it, which exert a spring force in the axial direction on the motor shaft and as a result, eliminate the axial play in the motor shaft. The spring element according to the invention has the advantage that it can be simply and inexpensively manufactured, for example by injection molding it, in particular out of plastic. Another advantage is the installation of the spring element according to the invention by simply sliding a single part onto the motor shaft. With the spring element according to the invention, the motor shaft is prestressed axially with a small amount of force and is secured in a particular position. Operating noise due to the axial play in the motor shaft is eliminated and noise during a change in the rotation direction is sharply reduced or possibly even eliminated. Axial vibrations of the motor shaft are also prevented. In addition, the spring element according to the invention compensates for different thermal expansions of the motor housing and motor shaft.
Advantageous embodiments and improvements of the invention disclosed in the main claim are the subjects of the dependent claims.